A tank-venting apparatus is disclosed in U.S. Pat. No. 4,962,744. This tank-venting apparatus includes the features of: an adsorption filter having a connecting line from the intake end of the filter to the intake pipe of the internal combustion engine with a supply line to the tank and with a venting opening; a tank-venting valve which is connected into the connecting line; a temperature sensor in the adsorption material for measuring temperature changes thereof based on adsorption or desorption; and, a control arrangement for controlling the tank-venting valve and for evaluating the signals of the temperature sensor.
A method for checking the operability of the tank-venting apparatus configured as described above includes the following steps: measuring the temperature of the adsorption material at the beginning of a tanking operation; measuring the temperature of the adsorption material at the end of the tanking operation; forming the adsorption-temperature difference between the first and second measured values; comparing the adsorption-temperature difference with a threshold value; and, determining that portion of the apparatus between the tank and the adsorption filter as operable when the adsorption temperature difference exceeds a threshold value.
According to another embodiment of the invention, the method includes the steps of: measuring the temperature of the adsorption material before the first regeneration of the material after a tanking operation; measuring the temperature of the adsorption material at a pregiven time point after start of the first regeneration; forming the material temperature difference between the first and second measured values; and, deciding that the apparatus is operable when the material temperature difference exceeds a second threshold value.
The arrangement corresponding to the above methods for checking the operability of the tank-venting apparatus described initially includes a control arrangement which is so configured that this arrangement carries out the above-mentioned method steps.